AppX Deployment Service EUVD-2026-99124

Exploitation requires an already-authenticated local user (PR:L, AV:L) on an affected Windows build and the ability to influence a filesystem path processed by the AppX Deployment Service so a symbolic link or junction can be followed to a file outside the attacker's privilege boundary. The high attack complexity (AC:H) indicates a non-trivial limiting factor - typically a race condition or specific pre-existing path/state the attacker must arrange and win - rather than reliable one-shot exploitation. Exploitation is bounded to local, authenticated contexts: there is no network vector, no privilege-escalation or integrity/availability impact (I:N/A:N), and impact is confined to disclosure of file contents (C:H). No user interaction from a victim is required (UI:N).

This is a genuinely low-priority vulnerability despite its CRITICAL-looking confidentiality impact (C:H). All signals align consistently toward low real-world risk: the CVSS 3.1 base score is 4.7 (Medium), the vector is local-only (AV:L) with high attack complexity (AC:H) and requires an authenticated local user (PR:L). CISA's SSVC decision framework reinforces this - Exploitation: none, Automatable: no, Technical Impact: partial - meaning no observed exploitation and the flaw cannot be reliably automated at scale. There is no CISA KEV listing and no public exploit identified at time of analysis, so this is not confirmed as actively exploited. No EPSS score was provided in the input, so probabilistic exploitation likelihood cannot be quantified here. The AC:H link-following (CWE-59) nature means an attacker must typically win a filesystem race or satisfy specific timing/path conditions to redirect the AppX Deployment Service into disclosing data it should not. In short, the only high metric is confidentiality impact; every exploitability signal (local vector, high complexity, required privileges, no automation, no known exploitation) points to a hard-to-weaponize, low-urgency issue best handled via routine Patch Tuesday cycles rather than emergency remediation.

A logged-in local user with standard privileges plants a malicious symbolic link or junction in a path consumed by the Windows AppX Deployment Service, then wins a timing/race window so the service follows the link and reads a file the attacker could not otherwise access, disclosing its contents. Because the attack requires local access, specific link placement, and winning a race (AC:H), reliable exploitation is difficult. No public exploit code was identified in the provided data.